Control of induction-motors.



No. 673,854. Patenten my 23, |9ol. A. H. ARMSTRONG.

CONTROL OF INDUCTION MOTORS.

(Application med May 9, 1901.)

3 Sheets-Sheet l.

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N0. 678,854. Patented .luly 23, IQOI. A. H. ARMSTRONG. CONTROL OF INDUCTION MOTORS.

(Application led May 9, 1901.)

3 Sheets-Sheet 2.

` (No Model.)

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CONTROL OF INDUCTION MOTORS.

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UNITED STATES PATENT Y 'l EETCE'a ALBERT II. ARMSTRONG, OF SCHENECTADY, NEV YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, OF NEW YORK.

CONTROL OF INDUCTIONNIOTORS.

SPECIFICATION forming part of Letters Patent No. 678,854, dated July 23, 1901.

Application filed May 9, 1901.

To @ZZ whom, it may concern:

Beit known that I, ALBERT H. ARMSTRONG, c

a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in the Control of Induction-Motors, (Case No. 2,233,) of which the following is a specification.

My invention relates to control systems for alternating-current ind uction-motors, and has for its object to equalize the heating of such motors when they are operated in tandem. In the tandem connection the induced member of the motor which is connected to the source of supply operates to supply current to the inducing member of a second motor, the induced member of which is short-circuited on itself when there are but two motors in the motor equipment or connected to the inducing member of a third motor when there are more than two. When the motor equipment consists of two motors connected in tandem and driving a common load, both of the motors will operate at substantially one-half thek speed at which they would run if both were directly connected to the source of supply. With the motors operating thus at substantially half their normal speed the frequency of the currents flowing in the interconnected windings of the two motors will be substantially one-half the frequency of the currents supplied to the first motor in the tandem connection, and the frequency of the currents iiowing in the induced member of the second motor will be substantially Zero. The motor which is directly connected to the source of supply must of course carry the magnetizing-eurrent'for both machines. In addition since the full frequency and voltage of the source of supply are impressed upon the windings of its inducing member the core loss in this member will be a maximum and the core loss in the induced member half what it would be at zero speed. On the other I Serial No. 59,378. (No model.)

induced member will be nearly negligible. Thus the heating of the motor which is No. l in the tandem connection will be very large as compared with the heating of the motor which is No. 2. In the operation of electricrailway systems this is a matter of considerable importance, since it is frequently the practice to go up heavy grades with the motors connected in tandem. In such systems the energy loss in the No. l motor is often exceedingly large, and thismotor may even get dangerously hot when operating on a road having heavy grades, while the second motor remains comparatively cool.

My present invention is a method for equalizing the heating of induction-motors when connected in tandem; and the method consists in changing or transposing from time to time, as the conditions under which the motors are operated render it advisable, the relative positions of some or all of the motors in the tandem connection. When there are but two motors in the tandem connection, the change is made by transposing the connections of the inducing member of the first motor and the induced member of the second motor, so that part of the time one of the motors will be directly connected to the source, so that it will be No. l in the tandem connection, and part of the time will be supplied with current through the windings of the other motor, so that it will be motor No. 2 in the tandem connection. When more than two motors are employed, it is sufficient to change the connections of the end motors only.

My invention will be better understood by reference to the following description, taken in connection with the accompanying drawings, which illustrate some of the arrangements of apparatus which may be used in practicing my invention and which constitute the subject-matter of my application, Serial No. 54,849, filed April 8, 1901.

In Jthe drawings, Figure l is a diagram of one-half of the car-wiring and one controller for the tandem multiple control of two induction-motors, the controller being provided with an auxiliary commutating-switch arranged to change the connections of the motors at predetermined intervals, in accordance with the principles of my present invena tion. Figs. 2 and 3 are diagrams illustrating the motor-circuits for the tandem connection in the two operative positions of the auxiliary commutating-switch of the controller. Figs. 4, 5, and 6 are views showing the mechanical construction of a controller comprising the switches diagrammatically illustrated in Fig. 1. Fig. 7 is a diagram of a car-wiring and controllers, showing how my invention may be applied without providing the controllers with auxiliary commutating-switches. Fig. 8 is a diagram illustrating the motor-circuits for the tandem connection when one of `the controllers of Fig. 7 is in operation, and Fig. 9 is a corresponding diagram illustrating the motor circuits for the tandem connection when the other controller of Fig. 7 is in operation.

My invention may evidently be employed in a motor-control system in which the tandem connection is only one of a series of connections that may be made as well as in a system in which the motors are operated permanently in tandem, and I have chosen to illustrate the arrangements which I have devised for practicing my invention as applied to the tandem-multiple system constituting the subject-matter of my Patent No. 539,404, dated May 2l, 1895.

Referring to Fig. 1 of the drawings, M' and M2 represent the windings oi' two three-phase induction-motors, which are connected, by means of the conductors 1a to 17 and 23 to 29', to a source of supply and to a regulating resistance through the contacts of the controller C. This controller comprises two main controlling-switches P and RS, of which the former operates to control the power connections of the motors and the latter to reverse the direction of motion of the motors, and an auxiliary switch CS for changing the motor connections in a manner hereinafter described. All of these switches are shown with their fixed and movable contacts developed on a plain surface, as is customary in diagrammatically illustrating such structures. The arrangement of the contacts of the switch P is the same as I have shown in my Patent No. 539,404, above referred to. This switch operates to first connect the Windings of the motors M' and M2 in tandem with the maximum resistance in circuit with the induced member of the second motor, then to gradually cut out the resistance, then to change the connections from tandem to multiple with a maximum resistance in circuit with the induced members of both motors, and finally to gradually cut out this resistalice.

Inasmuch as my present invention pertains only to the tandem connection, I shall in the following description refer only to the first three positions of the power-switch I,in which the tandem connections are completed, reference being made to my aforesaid patent for 'an explanation of the connections made in the succeeding positions of this switch.

The reversing-switch RS operates only to reverse the connection between two of the motor-terminals and two of the terminals of the three-phase source of supply, thereby reversing the direction of rotation of the motors.

While I have shown in Fig. 1 only one controller C connected to the windings of the motors M and M2, it is to be understood that the complete equipment for a railway-car will comprehend two controllers C, one at each end of the car, as is customary in such equipments, the second controller being connected to the wires 1li. to 17and 23'to 29at the right of Fig. 1 in the same manner as the controller which is shown is connected.

The purposes of my present invention are carried out in the arrangement illustrated in Fig. 1 by a commutating-switch CS in each controller, which operates in one of its positions to connect the terminals of the motor Ml to those conductors which lead to the source of supply through the contacts of the power and reversing switches and the terminals of the motorh 2 to those conductors which lead through contacts on the power-switch to the short-circuiting resistances, and in its other position to reverse these connections, so that the terminals ot' the motor M2 will be connected to the source of supply and the terminals of the motor M to the short-circuiting resistances. These connections I have indicated in Figs. 2 and 3, the former ot' which illustrates the motor connections in the first operative position of the power-switch P when the iixed contacts of the commutating-switch CS are in engagement with the range of contacts marked g and the latter of which illustrates the connections for the same position of the power-switch P when the iixed contacts of the commutating-switch are in engagement with the range of contacts marked 71.. In order to trace these connections in Fig. 1, let it be supposed that the reversing-swtch RS is so thrown that its fixed contacts 18 to 2l are in engagement with the range of movable contacts a and that the commutating switch is so thrown that its fixed contacts 22 to 29 are in engagement with the range of contacts g. If now the power-switch P is moved into .its first operative position, in which position the iixed contacts 1 to 17, inclusive, lie along the line l 1, circuits may be traced as follows from the three conductors T, T, and G, which when the system is in operation are connected to the terminals of a three-phase source of supply, one of these connections being shown as a ground, for the reason that in the operation of electric railways, for which, as above stated, my invention is particularly adapted, it is customary to complete the circuit between one of the terminals ofthe three-phase source and one of the terminals of the motors on the cars through the rails and the carwheels, only two trolley-contacts being used: Starting from the conductor T, a circuit leads through the contacts land 3 of the switch P to IOO IIO

the conductor 3', thence through contacts 21 and 2O of the reversing-switch to the conductor 20', and through the contacts 22 and 23 of the commutating-switch to the conductor 23' and the terminal of the winding a' on the inducing member of the motor M'. From the conductor T' another circuit leads through the contacts 2 and 4 of the power-switch to the conductor 4', thence through contacts 19] and 1S on the reversing-switch to the conductor 1S', and through contacts 26 and 27 of the commntating-switch to conductor 27', to which the terminal of the winding b' of the motor M' is connected. The terminal of the winding c' is connected permanently to ground and through ground to the third terminal of the three-phase source. Two of the terminals of the winding on the induced member of the motor M', this winding being indicated by the lines d', e', andf', are connected, through the conductors 14' and 15', the contacts 14 to 17 of the controller, and the conduetors 16' and 17', to two of the terminals of the corresponding winding of motor M2, the third terminal of each of these windings being connected to a common ground. Two of the terminals of the remaining winding on the motor M2 are connected through the conductors 25' and 29' and the corresponding contacts of the commutating-switch to the conductors 5' and 6' and thence through the contacts 5 and 8 and 6 and 10 of the powerswitch to the resistances R' and R2. The third terminal of this winding is connected, through the ground connection and the contacts 7 and 12 of the power-switch, to a third resistance R2, the other terminals of these three resistances being connected together. It will thus be seen that with the commutating-switch in the position specified the two motors will be connected in tandem with one of the windings of the motor M', connected to the source of supply, and the corresponding winding of the motor M2 shortcircuited on itself, this connection being diagrammatically illustrated, as already stated, in Fig. 2. If, however, the commutatingswitch is so thrown that its fixed contacts 22 to 29, inclusive, are in engagement with the movable contacts marked h, the reversing-switch being supposed for convenience in tracing the circuits to remain in the same position with its fixed contacts 18 to 21 in engagement with the contacts marked CL, the circuits between the source of supply and the motors may be traced as follows, with the power-switch, as before, in its first operative position: Starting from the conductor T, a circuit leads, as before, through the contacts 1 and 3 of the power-'switch to the conductor 3' and through the contacts 21 and 2O of the reversing-switch to the conductor 20' andthe contact 22 of the commutating-switch. From this point, however, the circuit instead of continuing through the Contact 23, as before, is now completed through the contact 25 and conductor 25', thus leading to the terminal of the winding a2 of the motor M2. Similarly the circuit from the conductor T' may be traced through the contacts 2 and 4 ofthe power-switch to the conductor 4,thence through the contacts 19 and 18 of the reversing-switch to the conductor 18', and the contact 26 of the commutating-switch, from which point the circuitl is completed through the contact 29 and the conductor 29', to the terminal of the winding b2 of the motor M2, the terminal of the third winding c2 being permanently connected through ground to the remaining terminal of the source of supply. The connections between the winding d', e', and f' of the motor M' and the winding d2 e2 f2 ot' the motor M2 remain unchanged, and of the terminals of the winding a' b c', which before were connected to the source of supply, the first two are now connected through the conductors 23' and 27' and the contacts 23 and 27 of the commutating-switch to the conductors 5' and 6', which are in turn connected, through the contacts 5 and 8 and 6 and 10 of the power-switch, to the resistanoes R' and R2, the terminal of the winding c' being connected through ground to the third resistance R2. The connections above traced are illustrated in Fig. 3, in whichit will be noted that the motor M2, which in Fig. 2 is the second motor in the tandem connection, has now become the iirst motor connected to the source of supply.

The commutating-switch CS may be provided with an operating-handle, sol that it can be thrown from one to the other of its operative positions whenever the motorman considers it advisable to make such change, or the commutating-switch may be so arranged that it will be operated indirectly by one of the main controlling-switches. If it is to be operated indirectly, the mechanism by means of which it is actuated should be so chosen that the motor connections will be changed often enough to prevent any one of the motors from heating excessively, the particular arrangement desirable for any one system being determined by the conditions under which the motors are operated.

In electric-railway systems the condition of the grades along the route is the principal determining factor, and depending on the distribution and character of' the same the commutating-switch may be arranged to be operated by the power-switch each time that it is moved from its off position or every third or forth time, as the conditions under which the motors are operated seem to demand, or by the reversing-switch in case an infrequent operation of the commutatingswitch is sufficient to accomplish the desired results. If the commutating-switch is operated by the power-switch, the lnotor connections will ot` coursebe changed every time that the controller is moved from its off" to on position, or at least whenever a predetermined number of such movements-have been made. Such an arrangement will be IOO IIO

required wheneverthe grades are excessive and frequent, so that it is inadvisable to operate the motors over the whole route without change of connections. If the commutating-switches are arranged to be operated by the reversing-switches, the motor connections will be changed at the end of every round trip if the car is operatedV in one direction over the line Afrom one controller and in the other direction from the controller at the other end of the car, the change in connection being made at one or the other end of the line, according to the relative positions ofthe com mutating-switehes of the two controllers at the start. rIhus if the commutating-switches in the two controllers occupy relatively opposite positions when the car is in motion from one end of the route the transfer of the control to the controller at ihe other end of the car will throw the commutating-switch of that controller into a position such that it will connect the motors inthe same relation in the tandem. connection as they were previously connected by the commutating-switch of the other controller. If, however, the commutating-switches in the two controllers occupy the same relative positions when the car is starting out from one end of the route, the transfer of the control to the controller at the other end of the car will bring the commutating-switch into a position such that it will reverse the position of the motors in the tandem connection. If it is desired that the connections shall be changed at each end of the route, the functions of the contacts of the comm utatingswitches may he carried out by a proper relative arrangement of the contacts of the two power-switches, and in Fig. 4 of the drawings I have indicated such an arrangement.

The operating means for the comm utatingswitch which I have chosen for illustration in the present application is so arranged that the said switch will he thrown each time that the main controlling-switch with which it is operatively connected is operated; but evidently it might be arranged so as to he thrown only after a predetermined number of such movements have been completed.

Referring to Figs. d and 5 of the drawings, which illustrate the controller construction in so far as it relates to my present invention, A indicates a controller-casing in which are mounted the three controller drums or cylinders P, RS, and CS. These cylinders carry the rectangular contacts, which 'are shown in development in Fig. l and are arranged to be rotated, so that these contacts come into engagement with a series of fixed fingers correspondingtothe circular contacts shown in Fig. l. These lingers are mounted in the customary manner, and for this reason it has been deemed unnecessary to illustrate them in the figures showing the construction of the controller. The reversing-switch RS is thrown into one or the other of its operative positions by means of the handle RH.

The power-switch P is rotated by means of a controller-handle, the lower portion of which is shown at PH. The commutating-cylinder OS is mounted below the reversing-switch cylinder and is provided at its lower end with a cam-shaped plate D, having two adjacent notches n and o on the side toward the powencylinder. A spring s is fastened at one end to a pin p2 on the bracket E, which supports the lower bearing of the commutating-switch, and at its other end is fastened to a pin p on the commutatingswitch cylinder, these pins being so positioned that as the commutating-switch is moved from one to the other of its operative positions the spring will pass over the point about which the com imitating-cylinder rotates, and will thus operate to throw it forcibly into either one of its operative positions and hold it there until the actuating means is again op eraied. Stops Iv and 'v2 are provided 'forlimitiug the throw of the switch. The shaft of the switch P carries at its lower end a cam B, against which bearsthe head t of a member Ii, which is suitably supported in abearing in the upper end of abracket m, projecting from the base of the controller. The member I? carries at its outerend a pivoted pawl r, which is normally held in the position shown in the drawings by means ofthe spring members s2 s2. A spring s is provided for maintaining the head t of the member F always in engagement with the face of the cam B. The arrangement of the parts shown in Fig. 5 corresponds to the olf position of the main cylinder P. If now this cylinder is rotated right-handedly, the surface of the cam B will operate to force the pawl Tinto engagement with the notch o in the plate D on the base of the commutating-switch, and the commutating-switch will be rotated until the spring s' passes over the center of support of the commutating switch, after which the said switch will be thrown by the force of the spring into its other operative position. The switch will remain in this position throughout the movement of the controller, the member F, after it has once been moved 'forward by the cam B, being held in its forward position throughout the movement of the con troller until it is again returned to its otf position. The movement of the commutatingswitch from the position .shown in Fie". 5 into its other operative position will operate to bring the notch n into such a position that when the member F is again projected forward the pawl fr will engage the notch It and throw the commutating-switch back into the position shown in the drawings. Whenever, therefore, the power-cylinder P is returned to its off position and is again moved for- `ward the pawl r will engage one or the other of the notches n and o, according to the positition of the commutatingswitch and will throw the said switch into its other operative position. In Fig. 4 I have also indicated in dotted lines how the commutating IOO IIO

switch may be operated from the reversingswitch cylinder instead of from the powercylinder, and in Fig. 6 I have shown more in detail the mechanism which is illustrated in dotted lines in Fig. 4. Referring to this latter figure, G indicates a cam mounted on a shaft w, arranged to rotate with the reversing-switch. D is a notched plate similar in all respects to the plate D, (shown in Fig. 5;) but in this case it is mounted on the upper end of the commutating-switch cylinder' iustead of below it. H is a slotted member having at one end a pin t', adapted to engage the edge of the cam G, and at its other endapin r', adapted to engage one or the other ot the notches n and o. A spring s3 operates to maintain the pin t always in engagement with the cam G. This mechanism operates in the same manner as that shown in Fig. 5. When the reversing-switch is in its off position, the pin "rests in the notched portion of the cam G; but whenever it is moved in either direction into one of its operative positions the pin r is drawn into engagement with one or the other of the notches n and 0 and the commutating-switch is moved until the spring s3 passes over the pivot on which the switch turns and throws it into its operative position,

The use of a commutating-switch operatively connected to one of the main controlling-switches ot'each controller is preferable when the grades are excessive or frequent or whenever they are heavier in one direction of running than in the other; but when the grades are substantially equal in both directions or whenever they are infrequent it may be suiicient if the arrangement of the motors in the tandem connection is reversed at each end of the run. In the latter case the separate commutating-switch in each controller may be dispensed with and the connections may be so arranged that the contacts of the power-switch in one controller will perform the functions of one of the sets of contacts ot the commutating-switch, and the contacts of the power-switch in the other controller the functions ot' the other set. Such an arrangement is illustrated in-Fig. 7 of the drawings, in which I have shown the two motors M and M2 connected by suitable wiring to the contacts of the two controllers C and C2. As shown in this figure, each controller comprises a power-switch P and a reversing-switch RS, similar in construction to the corresponding switches shown in Fig. 1; but in place of the commutating-switch of Fig. 1 the wiring is so arranged that whenever the controller C is in operation the motor M will be motor No. 1 in the tandem connection, and whenever the controller C2 is in operation the motor M2 will be No. 1 in the tandem connection. This result is accomplished by re- Versely connecting the windings a b c and a2 b2 c2 of the motors to the two controllers. Supposing the reversing-switch RS of the controller C to be thrown into such a position that its fixed contacts 18 to 21, inclusive, are in engagement with the contacts marked a, if the power-switch of this controller is moved to its iirst operative position,with the fixed contacts l to 17, inclusive, lying along the line 1 1, the motor-circuits will be completed as follows: Starting from the conductor T, a circuit may be traced through the contacts 1 and 3 to the conductor 3', thence through contacts 21 and 20 of the reversing-switch to the terminal of the winding a of the motor M. Starting from the conductor T', a circuit may be traced through the contacts 2 and 4c to the conductor 4 and thence through contacts 19 and 18 of the reversing-switch to the terminal of the winding b of the motor M. The third circuit is through the common ground connection to which the source and the terminal of the winding c are connected. The windings d e'f and cl2 e2f2 are connected by the controller-contacts the same`as in the diagram of Fig. 1, and these connections need not therefore be described in connection with the present gure. The terminals of the windings a2 and bzof the motorM2 are connected through contacts 5 and 8 and 6 and 10 to the resistances R and R2, the terminal of the remaining winding c2 being connected through a common ground connection to the resistance R3. The connections above described are illustrated in Fig. 8 of the drawings, from which it will be seen that whenever the controller C is operated to connect the motors in tandem the motor M will be No. 1 in tandem connection. Supposing now that the controller C is thrown to its ott position and that the reversing-switch of the controller C2 is thrown into such a position that its contacts 18 to 21 engage with the contacts marked @,if the power-cylinder P of this controller is moved into its first operative position the motor-circuits will be so arranged that the motor Mzwill be No. 1 in the tandem connection. For tracing the circuits it will be seen that a circuit leads from the conductor T through the contacts 1 and 3 of the powerswitch to the conductor 3', thence through contacts 19 and 18 of the reversing-switch to the terminal of the winding a2 of the motor M2. A circuit from the conductor T leads through contacts 2 and et of the power-switch to the conductor 11', and thence through contacts 21 and 20 of the reversing-switch to the terminal of the winding b2 of the motor M2, the connection between the source and the terminals of the windings c2 being made through the common ground connection. The windings d', e', and f and d2 e2 f2 of the two motors will be connected the same as when the other controller was in operation; but the other winding of the motor M' will have its terminals connected through the controller-contacts and the ground connection to the resistances R4, R5, and R6 of the controller C2. The connections for the tandem position of this controller C2 are shown in Fig. 9

IOO

IIO

of the drawings, from which it will be seen induction-motors operated in tandem, which that the motor M2 is No. 1 in the tandem coneonsists in transposing from time to time the neetiou. connections of the inducing member of the XVhat I eiaim as new, and desire to secure rst motor and of the induced member of the I5 5 by Letters Patent of the United States, is last motor in the tandem connection.

1. The method of equalizing the heating of In Witness whereof I have hereunto set my induction-motors operated in tandem, which hand this 7th day of May, 1901.

consists in changing from time to time the ALBERT II. ARMSTRONG. relative positions of the motors in the tandem Witnesses: 1o connections. BENJAMIN B. I-IULL,

2. The method of equalzng the heating 0f MARGARET E. I/VOOLLEY. 

